A roll forming machine has a series of large powered rollers to progressively bend a sheet of metal as it passes therethrough. When the sheet of metal is bent by the rollers past its elastic limit, the metal tends to spring back towards its original shape when the sheet of metal is released. Compensation for this spring back effect may be made by bending the sheet of metal past its desired final shape so that the sheet of metal will have the approximate correct shape after it springs back towards its original shape. However, the magnitude of the spring back varies in accordance with the thickness of the material and its metallurgical properties. Lots of sheet metal can vary significantly as to both the metallurgical properties and the material thickness so as to prevent each lot of sheet metal from obtaining the approximate correct shape if compensation for the new lot is not made.
To improve product quality, it is necessary to reduce the dimensional variations of the sheets of metal. The reduction of dimensional variations has previously been obtained by manually adjusting rollers of a roll forming machine to provide varying amounts of overbending in accordance with the metallurgical properties and the material thickness of a particular lot of sheet metal. Because the required gaging and adjustment processes are tedious and inexact when performed manually, adjustment of the rollers of a roll forming machine has been performed infrequently. As a result, the desired quality of the roll formed part has not been obtained.
This problem of the bent sheet metal having the desired final shape after being bent by a roll forming machine is particularly noticeable where the bent surface of a roll formed part must have a specific relation to a separate part with which it cooperates. For example, the front flange of a refrigerator cabinet surrounding the refrigerator cabinet opening must be substantially flat to enable a gasket of a door of the refrigerator cabinet to seal effectively against the front flange.
The system and method of the present invention satisfactorily solves the spring back problem through automatically sensing the need for adjustment of a roller of a roll forming machine and performing the adjustment in a precise manner. The system and method of the present invention measures the angle between the adjacent surfaces of a roll formed part that constitute the front flange of the refrigerator cabinet and the adjacent refrigerator cabinet wall with which it is connected after fabrication of the roll formed part to determine whether the angle is within a predetermined angular range. If the angle between the adjacent surfaces of the roll formed part is not within the predetermined angular range, then a roller of the roll forming machine is automatically adjusted to obtain the desired angle between the adjacent surfaces of the roll formed part.